1. Field of Invention
This invention generally relates to systems for filtering particulate matter from gases. More particularly, the invention relates to improved methods and systems for supplying high-pressure blowback gas via a plenum to filter elements during the cleaning phase of a continuous process filtration system.
2. Description of Related Art
Many industrial processes require the ability to remove particulate matter from gases. Examples include removing carbon and ash from a combustion exhaust stream prior to using the exhaust stream in a turbine, the recovery of catalyst used in a crude oil refining and petrochemical processes, and even the recovery of aroma particles during the processing of coffee products. Filtration systems that remove particulate matter from gases generally operate in one of two basic modes, namely as trap filters or continuous process filters. In their typical operating mode both designs function in a similar fashion: gas flows through the filter media, which retains the particulate matter, while the cleaned gas passes through the filter element and is passed onto the next stage of the overall process. Over time, the particulate matter builds up on the filter element, as a permeable cake of particulate matter, and the filter element will eventually require cleaning.
Trap, or final, filters are used on basically clean streams of gas where the objective is the protection of downstream processes and equipment. These filters are not intended for in-situ cleaning, and removal of the particulate matter from the filter requires the shutdown of the process and disassembly of the filter assembly. The filter elements are generally cleaned using chemical or ultrasonic methods.
Continuous process filters are used on heavily particulate laden streams of gas. As noted above, over time the particulate matter builds up on the filter element. Eventually the cake of particulate matter on the filter element will restrict the flow of gas through the filter media to such a degree that the filter element will require cleaning. At this point, a flow of high pressure blowback gas is fed through the filter elements in the reverse direction from the normal flow of gas, which forces the cake of particulate matter off of the filter element. At this point the cake falls to the bottom of the filter assembly. When a sufficient amount of particulate matter has been collected the filtered material is removed (discharged) from the filter assembly.
The overall filtration process need not be stopped during the cleaning process. The high-pressure blowback gas can be passed through a manifold and set of header pipes. This allows the high-pressure blowback gas to be directed to subsets of filter elements for cleaning. The remaining filter elements continue to function normally, filtering the dirty gas. The blowback gas is sequentially directed at the filter elements, such that all the filter elements are cleaned during a cleaning cycle. During a cleaning cycle the overall gas filtration process is operating sub optimally, due to the reverse flow of high-pressure blowback gas through a subset of the filter elements. However, this is still more efficient than shutting down the overall gas filtration process entirely during a cleaning cycle.